You don’t need to own the Limited Edition to complete Destiny 2 anymore
If you navigate to the triumph viewer and check out the Moments of Triumph subheader under the Account tab, you’ll find that the Limited Edition triumph is indeed gone. This particular subset of triumphs is supposed to be available in limited circumstances, with goals like completing content in Destiny 1. This was the only Moment of Triumph that had remained in the list whether you’d acquired it or not.
But you may not have it, even if you properly own the Destiny 2 Limited Edition. The triumph has been bugged from the start, with many players never receiving it – just check the Reddit thread. In the latest batch of known issues, Bungie says “we are investigating reports of players being unable to claim the ‘Limited Edition’ triumph.”
So the triumph may just be temporarily disabled while Bungie gets a fix out – though hopefully, that fix will keep it from continuing to appear incomplete in everybody’s triumph lists and save completionists some headaches. Either way, it’ll remain a 0 point item that offers no benefit aside from another tick on a checklist.